This invention is directed to microprocessor interrupt methods and is more specifically directed to handling multiple interrupt requests which occur in a short time interval as compared with the microprocessor speed.
Various types of microprocessor interrupt methods are known. In one method the microprocessor upon receiving an interrupt request polls a plurality of connected devices to determine which device initiated the request. This allows the microprocessor to serve a plurality of connected devices, but is inefficient in that the polling sequence may be time consuming. Such inefficiencies are especially evident in "bursty" data handling systems in which a plurality of interrupts occur within a short time interval.
Microprocessors such as the Motorola 68000 processor allow a vector interrupt method. In this method the microprocessor upon receiving an interrupt request also reads certain information on a bus and interprets such information as a vector. The microprocessor contains a predetermined table of software directives. The vector identifies one such directive which is then executed by the microprocessor. Upon completion of the interrupt handling program pointed to by the microprocessor directive, control is returned to the operating software environment for further processing including further interrupt handling. This method handles interrupts on an event by event basis.
Although the vector interrupt method represents an improvement over the polling interrupt method for bursty interrupt environments, a substantial amount of overhead processing time is used to handle interrupt requests in close time proximity requiring multiple reentries to the interrupt handler. Thus, there exists a need for an improved interrupt handling method which maximizes the ability of a microprocessor to respond to a plurality of closely spaced interrupt requests.